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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Cache loaders
*
* This file is part of Moodle's cache API, affectionately called MUC.
* It contains the components that are required in order to use caching.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
defined('MOODLE_INTERNAL') || die();
/**
* The main cache class.
*
* This class if the first class that any end developer will interact with.
* In order to create an instance of a cache that they can work with they must call one of the static make methods belonging
* to this class.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cache implements cache_loader {
/**
* We need a timestamp to use within the cache API.
* This stamp needs to be used for all ttl and time based operations to ensure that we don't end up with
* timing issues.
* @var int
*/
protected static $now;
/**
* A purge token used to distinguish between multiple cache purges in the same second.
* This is in the format <microtime>-<random string>.
*
* @var string
*/
protected static $purgetoken;
/**
* The definition used when loading this cache if there was one.
* @var cache_definition
*/
private $definition = false;
/**
* The cache store that this loader will make use of.
* @var cache_store
*/
private $store;
/**
* The next cache loader in the chain if there is one.
* If a cache request misses for the store belonging to this loader then the loader
* stored here will be checked next.
* If there is a loader here then $datasource must be false.
* @var cache_loader|false
*/
private $loader = false;
/**
* The data source to use if we need to load data (because if doesn't exist in the cache store).
* If there is a data source here then $loader above must be false.
* @var cache_data_source|false
*/
private $datasource = false;
/**
* Used to quickly check if the store supports key awareness.
* This is set when the cache is initialised and is used to speed up processing.
* @var bool
*/
private $supportskeyawareness = null;
/**
* Used to quickly check if the store supports ttl natively.
* This is set when the cache is initialised and is used to speed up processing.
* @var bool
*/
private $supportsnativettl = null;
/**
* Gets set to true if the cache is going to be using a static array for acceleration.
* The array statically caches items used during the lifetime of the request. This greatly speeds up interaction
* with the cache in areas where it will be repetitively hit for the same information such as with strings.
* There are several other variables to control how this static acceleration array works.
* @var bool
*/
private $staticacceleration = false;
/**
* The static acceleration array.
* Items will be stored in this cache as they were provided. This ensure there is no unnecessary processing taking place.
* @var array
*/
private $staticaccelerationarray = array();
/**
* The number of items in the static acceleration array. Avoids count calls like you wouldn't believe.
* @var int
*/
private $staticaccelerationcount = 0;
/**
* An array containing just the keys being used in the static acceleration array.
* This seems redundant perhaps but is used when managing the size of the static acceleration array.
* Items are added to the end of the array and the when we need to reduce the size of the cache we use the
* key that is first on this array.
* @var array
*/
private $staticaccelerationkeys = array();
/**
* The maximum size of the static acceleration array.
*
* If set to false there is no max size.
* Caches that make use of static acceleration should seriously consider setting this to something reasonably small, but
* still large enough to offset repetitive calls.
*
* @var int|false
*/
private $staticaccelerationsize = false;
/**
* Gets set to true during initialisation if the definition is making use of a ttl.
* Used to speed up processing.
* @var bool
*/
private $hasattl = false;
/**
* Gets set to the class name of the store during initialisation. This is used several times in the cache class internally
* and having it here helps speed up processing.
* @var strubg
*/
protected $storetype = 'unknown';
/**
* Gets set to true if we want to collect performance information about the cache API.
* @var bool
*/
protected $perfdebug = false;
/**
* Determines if this loader is a sub loader, not the top of the chain.
* @var bool
*/
protected $subloader = false;
/**
* Creates a new cache instance for a pre-defined definition.
*
* @param string $component The component for the definition
* @param string $area The area for the definition
* @param array $identifiers Any additional identifiers that should be provided to the definition.
* @param string $unused Used to be datasourceaggregate but that was removed and this is now unused.
* @return cache_application|cache_session|cache_store
*/
public static function make($component, $area, array $identifiers = array(), $unused = null) {
$factory = cache_factory::instance();
return $factory->create_cache_from_definition($component, $area, $identifiers);
}
/**
* Creates a new cache instance based upon the given params.
*
* @param int $mode One of cache_store::MODE_*
* @param string $component The component this cache relates to.
* @param string $area The area this cache relates to.
* @param array $identifiers Any additional identifiers that should be provided to the definition.
* @param array $options An array of options, available options are:
* - simplekeys : Set to true if the keys you will use are a-zA-Z0-9_
* - simpledata : Set to true if the type of the data you are going to store is scalar, or an array of scalar vars
* - staticacceleration : If set to true the cache will hold onto data passing through it.
* - staticaccelerationsize : The max size for the static acceleration array.
* @return cache_application|cache_session|cache_store
*/
public static function make_from_params($mode, $component, $area, array $identifiers = array(), array $options = array()) {
$factory = cache_factory::instance();
return $factory->create_cache_from_params($mode, $component, $area, $identifiers, $options);
}
/**
* Constructs a new cache instance.
*
* You should not call this method from your code, instead you should use the cache::make methods.
*
* This method is public so that the cache_factory is able to instantiate cache instances.
* Ideally we would make this method protected and expose its construction to the factory method internally somehow.
* The factory class is responsible for this in order to centralise the storage of instances once created. This way if needed
* we can force a reset of the cache API (used during unit testing).
*
* @param cache_definition $definition The definition for the cache instance.
* @param cache_store $store The store that cache should use.
* @param cache_loader|cache_data_source $loader The next loader in the chain or the data source if there is one and there
* are no other cache_loaders in the chain.
*/
public function __construct(cache_definition $definition, cache_store $store, $loader = null) {
global $CFG;
$this->definition = $definition;
$this->store = $store;
$this->storetype = get_class($store);
$this->perfdebug = (!empty($CFG->perfdebug) and $CFG->perfdebug > 7);
if ($loader instanceof cache_loader) {
$this->loader = $loader;
// Mark the loader as a sub (chained) loader.
$this->loader->set_is_sub_loader(true);
} else if ($loader instanceof cache_data_source) {
$this->datasource = $loader;
}
$this->definition->generate_definition_hash();
$this->staticacceleration = $this->definition->use_static_acceleration();
if ($this->staticacceleration) {
$this->staticaccelerationsize = $this->definition->get_static_acceleration_size();
}
$this->hasattl = ($this->definition->get_ttl() > 0);
}
/**
* Used to inform the loader of its state as a sub loader, or as the top of the chain.
*
* This is important as it ensures that we do not have more than one loader keeping static acceleration data.
* Subloaders need to be "pure" loaders in the sense that they are used to store and retrieve information from stores or the
* next loader/data source in the chain.
* Nothing fancy, nothing flash.
*
* @param bool $setting
*/
protected function set_is_sub_loader($setting = true) {
if ($setting) {
$this->subloader = true;
// Subloaders should not keep static acceleration data.
$this->staticacceleration = false;
$this->staticaccelerationsize = false;
} else {
$this->subloader = true;
$this->staticacceleration = $this->definition->use_static_acceleration();
if ($this->staticacceleration) {
$this->staticaccelerationsize = $this->definition->get_static_acceleration_size();
}
}
}
/**
* Alters the identifiers that have been provided to the definition.
*
* This is an advanced method and should not be used unless really needed.
* It allows the developer to slightly alter the definition without having to re-establish the cache.
* It will cause more processing as the definition will need to clear and reprepare some of its properties.
*
* @param array $identifiers
*/
public function set_identifiers(array $identifiers) {
if ($this->definition->set_identifiers($identifiers)) {
// As static acceleration uses input keys and not parsed keys
// it much be cleared when the identifier set is changed.
$this->staticaccelerationarray = array();
if ($this->staticaccelerationsize !== false) {
$this->staticaccelerationkeys = array();
$this->staticaccelerationcount = 0;
}
}
}
/**
* Process any outstanding invalidation events for the cache we are registering,
*
* Identifiers and event invalidation are not compatible with each other at this time.
* As a result the cache does not need to consider identifiers when working out what to invalidate.
*/
protected function handle_invalidation_events() {
if (!$this->definition->has_invalidation_events()) {
return;
}
// Each cache stores the current 'lastinvalidation' value within the cache itself.
$lastinvalidation = $this->get('lastinvalidation');
if ($lastinvalidation === false) {
// There is currently no value for the lastinvalidation token, therefore the token is not set, and there
// can be nothing to invalidate.
// Set the lastinvalidation value to the current purge token and return early.
$this->set('lastinvalidation', self::get_purge_token());
return;
} else if ($lastinvalidation == self::get_purge_token()) {
// The current purge request has already been fully handled by this cache.
return;
}
/*
* Now that the whole cache check is complete, we check the meaning of any specific cache invalidation events.
* These are stored in the core/eventinvalidation cache as an multi-dimensinoal array in the form:
* [
* eventname => [
* keyname => purgetoken,
* ]
* ]
*
* The 'keyname' value is used to delete a specific key in the cache.
* If the keyname is set to the special value 'purged', then the whole cache is purged instead.
*
* The 'purgetoken' is the token that this key was last purged.
* a) If the purgetoken matches the last invalidation, then the key/cache is not purged.
* b) If the purgetoken is newer than the last invalidation, then the key/cache is not purged.
* c) If the purge token is older than the last invalidation, or it has a different token component, then the
* cache is purged.
*
* Option b should not happen under normal operation, but may happen in race condition whereby a long-running
* request's cache is cleared in another process during that request, and prior to that long-running request
* creating the cache. In such a condition, it would be incorrect to clear that cache.
*/
$cache = self::make('core', 'eventinvalidation');
$events = $cache->get_many($this->definition->get_invalidation_events());
$todelete = array();
$purgeall = false;
// Iterate the returned data for the events.
foreach ($events as $event => $keys) {
if ($keys === false) {
// No data to be invalidated yet.
continue;
}
// Look at each key and check the timestamp.
foreach ($keys as $key => $purgetoken) {
// If the timestamp of the event is more than or equal to the last invalidation (happened between the last
// invalidation and now), then we need to invaliate the key.
if (self::compare_purge_tokens($purgetoken, $lastinvalidation) > 0) {
if ($key === 'purged') {
$purgeall = true;
break;
} else {
$todelete[] = $key;
}
}
}
}
if ($purgeall) {
$this->purge();
} else if (!empty($todelete)) {
$todelete = array_unique($todelete);
$this->delete_many($todelete);
}
// Set the time of the last invalidation.
if ($purgeall || !empty($todelete)) {
$this->set('lastinvalidation', self::get_purge_token(true));
}
}
/**
* Retrieves the value for the given key from the cache.
*
* @param string|int $key The key for the data being requested.
* It can be any structure although using a scalar string or int is recommended in the interests of performance.
* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
* @param int $strictness One of IGNORE_MISSING | MUST_EXIST
* @return mixed|false The data from the cache or false if the key did not exist within the cache.
* @throws coding_exception
*/
public function get($key, $strictness = IGNORE_MISSING) {
// 1. Get it from the static acceleration array if we can (only when it is enabled and it has already been requested/set).
$usesstaticacceleration = $this->use_static_acceleration();
if ($usesstaticacceleration) {
$result = $this->static_acceleration_get($key);
if ($result !== false) {
return $result;
}
}
// 2. Parse the key.
$parsedkey = $this->parse_key($key);
// 3. Get it from the store. Obviously wasn't in the static acceleration array.
$result = $this->store->get($parsedkey);
if ($result !== false) {
if ($result instanceof cache_ttl_wrapper) {
if ($result->has_expired()) {
$this->store->delete($parsedkey);
$result = false;
} else {
$result = $result->data;
}
}
if ($usesstaticacceleration) {
$this->static_acceleration_set($key, $result);
}
if ($result instanceof cache_cached_object) {
$result = $result->restore_object();
}
}
// 4. Load if from the loader/datasource if we don't already have it.
$setaftervalidation = false;
if ($result === false) {
if ($this->perfdebug) {
cache_helper::record_cache_miss($this->store, $this->definition);
}
if ($this->loader !== false) {
// We must pass the original (unparsed) key to the next loader in the chain.
// The next loader will parse the key as it sees fit. It may be parsed differently
// depending upon the capabilities of the store associated with the loader.
$result = $this->loader->get($key);
} else if ($this->datasource !== false) {
$result = $this->datasource->load_for_cache($key);
}
$setaftervalidation = ($result !== false);
} else if ($this->perfdebug) {
cache_helper::record_cache_hit($this->store, $this->definition);
}
// 5. Validate strictness.
if ($strictness === MUST_EXIST && $result === false) {
throw new coding_exception('Requested key did not exist in any cache stores and could not be loaded.');
}
// 6. Set it to the store if we got it from the loader/datasource.
if ($setaftervalidation) {
$this->set($key, $result);
}
// 7. Make sure we don't pass back anything that could be a reference.
// We don't want people modifying the data in the cache.
if (!$this->store->supports_dereferencing_objects() && !is_scalar($result)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$result = $this->unref($result);
}
return $result;
}
/**
* Retrieves an array of values for an array of keys.
*
* Using this function comes with potential performance implications.
* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
* the equivalent singular method for each item provided.
* This should not deter you from using this function as there is a performance benefit in situations where the cache store
* does support it, but you should be aware of this fact.
*
* @param array $keys The keys of the data being requested.
* Each key can be any structure although using a scalar string or int is recommended in the interests of performance.
* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.
* @return array An array of key value pairs for the items that could be retrieved from the cache.
* If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown.
* Otherwise any key that did not exist will have a data value of false within the results.
* @throws coding_exception
*/
public function get_many(array $keys, $strictness = IGNORE_MISSING) {
$keysparsed = array();
$parsedkeys = array();
$resultpersist = array();
$resultstore = array();
$keystofind = array();
// First up check the persist cache for each key.
$isusingpersist = $this->use_static_acceleration();
foreach ($keys as $key) {
$pkey = $this->parse_key($key);
if (is_array($pkey)) {
$pkey = $pkey['key'];
}
$keysparsed[$key] = $pkey;
$parsedkeys[$pkey] = $key;
$keystofind[$pkey] = $key;
if ($isusingpersist) {
$value = $this->static_acceleration_get($key);
if ($value !== false) {
$resultpersist[$pkey] = $value;
unset($keystofind[$pkey]);
}
}
}
// Next assuming we didn't find all of the keys in the persist cache try loading them from the store.
if (count($keystofind)) {
$resultstore = $this->store->get_many(array_keys($keystofind));
// Process each item in the result to "unwrap" it.
foreach ($resultstore as $key => $value) {
if ($value instanceof cache_ttl_wrapper) {
if ($value->has_expired()) {
$value = false;
} else {
$value = $value->data;
}
}
if ($value !== false && $this->use_static_acceleration()) {
$this->static_acceleration_set($keystofind[$key], $value);
}
if ($value instanceof cache_cached_object) {
$value = $value->restore_object();
}
$resultstore[$key] = $value;
}
}
// Merge the result from the persis cache with the results from the store load.
$result = $resultpersist + $resultstore;
unset($resultpersist);
unset($resultstore);
// Next we need to find any missing values and load them from the loader/datasource next in the chain.
$usingloader = ($this->loader !== false);
$usingsource = (!$usingloader && ($this->datasource !== false));
if ($usingloader || $usingsource) {
$missingkeys = array();
foreach ($result as $key => $value) {
if ($value === false) {
$missingkeys[] = $parsedkeys[$key];
}
}
if (!empty($missingkeys)) {
if ($usingloader) {
$resultmissing = $this->loader->get_many($missingkeys);
} else {
$resultmissing = $this->datasource->load_many_for_cache($missingkeys);
}
foreach ($resultmissing as $key => $value) {
$result[$keysparsed[$key]] = $value;
if ($value !== false) {
$this->set($key, $value);
}
}
unset($resultmissing);
}
unset($missingkeys);
}
// Create an array with the original keys and the found values. This will be what we return.
$fullresult = array();
foreach ($result as $key => $value) {
if (!is_scalar($value)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$value = $this->unref($value);
}
$fullresult[$parsedkeys[$key]] = $value;
}
unset($result);
// Final step is to check strictness.
if ($strictness === MUST_EXIST) {
foreach ($keys as $key) {
if (!array_key_exists($key, $fullresult)) {
throw new coding_exception('Not all the requested keys existed within the cache stores.');
}
}
}
if ($this->perfdebug) {
$hits = 0;
$misses = 0;
foreach ($fullresult as $value) {
if ($value === false) {
$misses++;
} else {
$hits++;
}
}
cache_helper::record_cache_hit($this->store, $this->definition, $hits);
cache_helper::record_cache_miss($this->store, $this->definition, $misses);
}
// Return the result. Phew!
return $fullresult;
}
/**
* Sends a key => value pair to the cache.
*
* <code>
* // This code will add four entries to the cache, one for each url.
* $cache->set('main', 'http://moodle.org');
* $cache->set('docs', 'http://docs.moodle.org');
* $cache->set('tracker', 'http://tracker.moodle.org');
* $cache->set('qa', 'http://qa.moodle.net');
* </code>
*
* @param string|int $key The key for the data being requested.
* It can be any structure although using a scalar string or int is recommended in the interests of performance.
* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
* @param mixed $data The data to set against the key.
* @return bool True on success, false otherwise.
*/
public function set($key, $data) {
if ($this->perfdebug) {
cache_helper::record_cache_set($this->store, $this->definition);
}
if ($this->loader !== false) {
// We have a loader available set it there as well.
// We have to let the loader do its own parsing of data as it may be unique.
$this->loader->set($key, $data);
}
$usestaticacceleration = $this->use_static_acceleration();
if (is_object($data) && $data instanceof cacheable_object) {
$data = new cache_cached_object($data);
} else if (!$this->store->supports_dereferencing_objects() && !is_scalar($data)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$data = $this->unref($data);
}
if ($usestaticacceleration) {
$this->static_acceleration_set($key, $data);
}
if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {
$data = new cache_ttl_wrapper($data, $this->definition->get_ttl());
}
$parsedkey = $this->parse_key($key);
return $this->store->set($parsedkey, $data);
}
/**
* Removes references where required.
*
* @param stdClass|array $data
* @return mixed What ever was put in but without any references.
*/
protected function unref($data) {
if ($this->definition->uses_simple_data()) {
return $data;
}
// Check if it requires serialisation in order to produce a reference free copy.
if ($this->requires_serialisation($data)) {
// Damn, its going to have to be serialise.
$data = serialize($data);
// We unserialise immediately so that we don't have to do it every time on get.
$data = unserialize($data);
} else if (!is_scalar($data)) {
// Its safe to clone, lets do it, its going to beat the pants of serialisation.
$data = $this->deep_clone($data);
}
return $data;
}
/**
* Checks to see if a var requires serialisation.
*
* @param mixed $value The value to check.
* @param int $depth Used to ensure we don't enter an endless loop (think recursion).
* @return bool Returns true if the value is going to require serialisation in order to ensure a reference free copy
* or false if its safe to clone.
*/
protected function requires_serialisation($value, $depth = 1) {
if (is_scalar($value)) {
return false;
} else if (is_array($value) || $value instanceof stdClass || $value instanceof Traversable) {
if ($depth > 5) {
// Skrew it, mega-deep object, developer you suck, we're just going to serialise.
return true;
}
foreach ($value as $key => $subvalue) {
if ($this->requires_serialisation($subvalue, $depth++)) {
return true;
}
}
}
// Its not scalar, array, or stdClass so we'll need to serialise.
return true;
}
/**
* Creates a reference free clone of the given value.
*
* @param mixed $value
* @return mixed
*/
protected function deep_clone($value) {
if (is_object($value)) {
// Objects must be cloned to begin with.
$value = clone $value;
}
if (is_array($value) || is_object($value)) {
foreach ($value as $key => $subvalue) {
$value[$key] = $this->deep_clone($subvalue);
}
}
return $value;
}
/**
* Sends several key => value pairs to the cache.
*
* Using this function comes with potential performance implications.
* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
* the equivalent singular method for each item provided.
* This should not deter you from using this function as there is a performance benefit in situations where the cache store
* does support it, but you should be aware of this fact.
*
* <code>
* // This code will add four entries to the cache, one for each url.
* $cache->set_many(array(
* 'main' => 'http://moodle.org',
* 'docs' => 'http://docs.moodle.org',
* 'tracker' => 'http://tracker.moodle.org',
* 'qa' => ''http://qa.moodle.net'
* ));
* </code>
*
* @param array $keyvaluearray An array of key => value pairs to send to the cache.
* @return int The number of items successfully set. It is up to the developer to check this matches the number of items.
* ... if they care that is.
*/
public function set_many(array $keyvaluearray) {
if ($this->loader !== false) {
// We have a loader available set it there as well.
// We have to let the loader do its own parsing of data as it may be unique.
$this->loader->set_many($keyvaluearray);
}
$data = array();
$simulatettl = $this->has_a_ttl() && !$this->store_supports_native_ttl();
$usestaticaccelerationarray = $this->use_static_acceleration();
$needsdereferencing = !$this->store->supports_dereferencing_objects();
foreach ($keyvaluearray as $key => $value) {
if (is_object($value) && $value instanceof cacheable_object) {
$value = new cache_cached_object($value);
} else if ($needsdereferencing && !is_scalar($value)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$value = $this->unref($value);
}
if ($usestaticaccelerationarray) {
$this->static_acceleration_set($key, $value);
}
if ($simulatettl) {
$value = new cache_ttl_wrapper($value, $this->definition->get_ttl());
}
$data[$key] = array(
'key' => $this->parse_key($key),
'value' => $value
);
}
$successfullyset = $this->store->set_many($data);
if ($this->perfdebug && $successfullyset) {
cache_helper::record_cache_set($this->store, $this->definition, $successfullyset);
}
return $successfullyset;
}
/**
* Test is a cache has a key.
*
* The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the
* test and any subsequent action (get, set, delete etc).
* Instead it is recommended to write your code in such a way they it performs the following steps:
* <ol>
* <li>Attempt to retrieve the information.</li>
* <li>Generate the information.</li>
* <li>Attempt to set the information</li>
* </ol>
*
* Its also worth mentioning that not all stores support key tests.
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
* Just one more reason you should not use these methods unless you have a very good reason to do so.
*
* @param string|int $key
* @param bool $tryloadifpossible If set to true, the cache doesn't contain the key, and there is another cache loader or
* data source then the code will try load the key value from the next item in the chain.
* @return bool True if the cache has the requested key, false otherwise.
*/
public function has($key, $tryloadifpossible = false) {
if ($this->static_acceleration_has($key)) {
// Hoorah, that was easy. It exists in the static acceleration array so we definitely have it.
return true;
}
$parsedkey = $this->parse_key($key);
if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {
// The data has a TTL and the store doesn't support it natively.
// We must fetch the data and expect a ttl wrapper.
$data = $this->store->get($parsedkey);
$has = ($data instanceof cache_ttl_wrapper && !$data->has_expired());
} else if (!$this->store_supports_key_awareness()) {
// The store doesn't support key awareness, get the data and check it manually... puke.
// Either no TTL is set of the store supports its handling natively.
$data = $this->store->get($parsedkey);
$has = ($data !== false);
} else {
// The store supports key awareness, this is easy!
// Either no TTL is set of the store supports its handling natively.
$has = $this->store->has($parsedkey);
}
if (!$has && $tryloadifpossible) {
if ($this->loader !== false) {
$result = $this->loader->get($parsedkey);
} else if ($this->datasource !== null) {
$result = $this->datasource->load_for_cache($key);
}
$has = ($result !== null);
if ($has) {
$this->set($key, $result);
}
}
return $has;
}
/**
* Test is a cache has all of the given keys.
*
* It is strongly recommended to avoid the use of this function if not absolutely required.
* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
*
* Its also worth mentioning that not all stores support key tests.
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
* Just one more reason you should not use these methods unless you have a very good reason to do so.
*
* @param array $keys
* @return bool True if the cache has all of the given keys, false otherwise.
*/
public function has_all(array $keys) {
if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {
foreach ($keys as $key) {
if (!$this->has($key)) {
return false;
}
}
return true;
}
$parsedkeys = array_map(array($this, 'parse_key'), $keys);
return $this->store->has_all($parsedkeys);
}
/**
* Test if a cache has at least one of the given keys.
*
* It is strongly recommended to avoid the use of this function if not absolutely required.
* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
*
* Its also worth mentioning that not all stores support key tests.
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
* Just one more reason you should not use these methods unless you have a very good reason to do so.
*
* @param array $keys
* @return bool True if the cache has at least one of the given keys
*/
public function has_any(array $keys) {
if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {
foreach ($keys as $key) {
if ($this->has($key)) {
return true;
}
}
return false;
}
if ($this->use_static_acceleration()) {
foreach ($keys as $id => $key) {
if ($this->static_acceleration_has($key)) {
return true;
}
}
}
$parsedkeys = array_map(array($this, 'parse_key'), $keys);
return $this->store->has_any($parsedkeys);
}
/**
* Delete the given key from the cache.
*
* @param string|int $key The key to delete.
* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
* @return bool True of success, false otherwise.
*/
public function delete($key, $recurse = true) {
$this->static_acceleration_delete($key);
if ($recurse && $this->loader !== false) {
// Delete from the bottom of the stack first.
$this->loader->delete($key, $recurse);
}
$parsedkey = $this->parse_key($key);
return $this->store->delete($parsedkey);
}
/**
* Delete all of the given keys from the cache.
*
* @param array $keys The key to delete.
* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
* @return int The number of items successfully deleted.
*/
public function delete_many(array $keys, $recurse = true) {
if ($this->use_static_acceleration()) {
foreach ($keys as $key) {
$this->static_acceleration_delete($key);
}
}
if ($recurse && $this->loader !== false) {
// Delete from the bottom of the stack first.
$this->loader->delete_many($keys, $recurse);
}
$parsedkeys = array_map(array($this, 'parse_key'), $keys);
return $this->store->delete_many($parsedkeys);
}
/**
* Purges the cache store, and loader if there is one.
*
* @return bool True on success, false otherwise
*/
public function purge() {
// 1. Purge the static acceleration array.
$this->static_acceleration_purge();
// 2. Purge the store.
$this->store->purge();
// 3. Optionally pruge any stacked loaders.
if ($this->loader) {
$this->loader->purge();
}
return true;
}
/**
* Parses the key turning it into a string (or array is required) suitable to be passed to the cache store.
*
* @param string|int $key As passed to get|set|delete etc.
* @return string|array String unless the store supports multi-identifiers in which case an array if returned.
*/
protected function parse_key($key) {
// First up if the store supports multiple keys we'll go with that.
if ($this->store->supports_multiple_identifiers()) {
$result = $this->definition->generate_multi_key_parts();
$result['key'] = $key;
return $result;
}
// If not we need to generate a hash and to for that we use the cache_helper.
return cache_helper::hash_key($key, $this->definition);
}
/**
* Returns true if the cache is making use of a ttl.
* @return bool
*/
protected function has_a_ttl() {
return $this->hasattl;
}
/**
* Returns true if the cache store supports native ttl.
* @return bool
*/
protected function store_supports_native_ttl() {
if ($this->supportsnativettl === null) {
$this->supportsnativettl = ($this->store->supports_native_ttl());
}
return $this->supportsnativettl;
}
/**
* Returns the cache definition.
*
* @return cache_definition
*/
protected function get_definition() {
return $this->definition;
}
/**
* Returns the cache store
*
* @return cache_store
*/
protected function get_store() {
return $this->store;
}
/**
* Returns the loader associated with this instance.
*
* @since Moodle 2.4.4
* @return cache|false
*/
protected function get_loader() {
return $this->loader;
}
/**
* Returns the data source associated with this cache.
*
* @since Moodle 2.4.4
* @return cache_data_source|false
*/
protected function get_datasource() {
return $this->datasource;
}
/**
* Returns true if the store supports key awareness.
*
* @return bool
*/
protected function store_supports_key_awareness() {
if ($this->supportskeyawareness === null) {
$this->supportskeyawareness = ($this->store instanceof cache_is_key_aware);
}
return $this->supportskeyawareness;
}
/**
* Returns true if the store natively supports locking.
*
* @return bool
*/
protected function store_supports_native_locking() {
if ($this->nativelocking === null) {
$this->nativelocking = ($this->store instanceof cache_is_lockable);
}
return $this->nativelocking;
}
/**
* @deprecated since 2.6
* @see cache::use_static_acceleration()
*/
protected function is_using_persist_cache() {
throw new coding_exception('cache::is_using_persist_cache() can not be used anymore.' .
' Please use cache::use_static_acceleration() instead.');
}
/**
* Returns true if this cache is making use of the static acceleration array.
*
* @return bool
*/
protected function use_static_acceleration() {
return $this->staticacceleration;
}
/**
* @see cache::static_acceleration_has
* @deprecated since 2.6
*/
protected function is_in_persist_cache() {
throw new coding_exception('cache::is_in_persist_cache() can not be used anymore.' .
' Please use cache::static_acceleration_has() instead.');
}
/**
* Returns true if the requested key exists within the static acceleration array.
*
* @param string $key The parsed key
* @return bool
*/
protected function static_acceleration_has($key) {
// This could be written as a single line, however it has been split because the ttl check is faster than the instanceof
// and has_expired calls.
if (!$this->staticacceleration || !isset($this->staticaccelerationarray[$key])) {
return false;
}
return true;
}
/**
* @deprecated since 2.6
* @see cache::static_acceleration_get
*/
protected function get_from_persist_cache() {
throw new coding_exception('cache::get_from_persist_cache() can not be used anymore.' .
' Please use cache::static_acceleration_get() instead.');
}
/**
* Returns the item from the static acceleration array if it exists there.
*
* @param string $key The parsed key
* @return mixed|false Dereferenced data from the static acceleration array or false if it wasn't there.
*/
protected function static_acceleration_get($key) {
if (!$this->staticacceleration || !isset($this->staticaccelerationarray[$key])) {
$result = false;
} else {
$data = $this->staticaccelerationarray[$key]['data'];
if ($data instanceof cache_cached_object) {
$result = $data->restore_object();
} else if ($this->staticaccelerationarray[$key]['serialized']) {
$result = unserialize($data);
} else {
$result = $data;
}
}
if ($result !== false) {
if ($this->perfdebug) {
cache_helper::record_cache_hit(cache_store::STATIC_ACCEL, $this->definition);
}
if ($this->staticaccelerationsize > 1 && $this->staticaccelerationcount > 1) {
// Check to see if this is the last item on the static acceleration keys array.
if (end($this->staticaccelerationkeys) !== $key) {
// It isn't the last item.
// Move the item to the end of the array so that it is last to be removed.
unset($this->staticaccelerationkeys[$key]);
$this->staticaccelerationkeys[$key] = $key;
}
}
return $result;
} else {
if ($this->perfdebug) {
cache_helper::record_cache_miss(cache_store::STATIC_ACCEL, $this->definition);
}
return false;
}
}
/**
* @deprecated since 2.6
* @see cache::static_acceleration_set
*/
protected function set_in_persist_cache() {
throw new coding_exception('cache::set_in_persist_cache() can not be used anymore.' .
' Please use cache::static_acceleration_set() instead.');
}
/**
* Sets a key value pair into the static acceleration array.
*
* @param string $key The parsed key
* @param mixed $data
* @return bool
*/
protected function static_acceleration_set($key, $data) {
if ($this->staticaccelerationsize !== false && isset($this->staticaccelerationkeys[$key])) {
$this->staticaccelerationcount--;
unset($this->staticaccelerationkeys[$key]);
}
// We serialize anything that's not;
// 1. A known scalar safe value.
// 2. A definition that says it's simpledata. We trust it that it doesn't contain dangerous references.
// 3. An object that handles dereferencing by itself.
if (is_scalar($data) || $this->definition->uses_simple_data()
|| $data instanceof cache_cached_object) {
$this->staticaccelerationarray[$key]['data'] = $data;
$this->staticaccelerationarray[$key]['serialized'] = false;
} else {
$this->staticaccelerationarray[$key]['data'] = serialize($data);
$this->staticaccelerationarray[$key]['serialized'] = true;
}
if ($this->staticaccelerationsize !== false) {
$this->staticaccelerationcount++;
$this->staticaccelerationkeys[$key] = $key;
if ($this->staticaccelerationcount > $this->staticaccelerationsize) {
$dropkey = array_shift($this->staticaccelerationkeys);
unset($this->staticaccelerationarray[$dropkey]);
$this->staticaccelerationcount--;
}
}
return true;
}
/**
* @deprecated since 2.6
* @see cache::static_acceleration_delete()
*/
protected function delete_from_persist_cache() {
throw new coding_exception('cache::delete_from_persist_cache() can not be used anymore.' .
' Please use cache::static_acceleration_delete() instead.');
}
/**
* Deletes an item from the static acceleration array.
*
* @param string|int $key As given to get|set|delete
* @return bool True on success, false otherwise.
*/
protected function static_acceleration_delete($key) {
unset($this->staticaccelerationarray[$key]);
if ($this->staticaccelerationsize !== false && isset($this->staticaccelerationkeys[$key])) {
unset($this->staticaccelerationkeys[$key]);
$this->staticaccelerationcount--;
}
return true;
}
/**
* Purge the static acceleration cache.
*/
protected function static_acceleration_purge() {
$this->staticaccelerationarray = array();
if ($this->staticaccelerationsize !== false) {
$this->staticaccelerationkeys = array();
$this->staticaccelerationcount = 0;
}
}
/**
* Returns the timestamp from the first request for the time from the cache API.
*
* This stamp needs to be used for all ttl and time based operations to ensure that we don't end up with
* timing issues.
*
* @param bool $float Whether to use floating precision accuracy.
* @return int|float
*/
public static function now($float = false) {
if (self::$now === null) {
self::$now = microtime(true);
}
if ($float) {
return self::$now;
} else {
return (int) self::$now;
}
}
/**
* Get a 'purge' token used for cache invalidation handling.
*
* Note: This function is intended for use from within the Cache API only and not by plugins, or cache stores.
*
* @param bool $reset Whether to reset the token and generate a new one.
* @return string
*/
public static function get_purge_token($reset = false) {
if (self::$purgetoken === null || $reset) {
self::$now = null;
self::$purgetoken = self::now(true) . '-' . uniqid('', true);
}
return self::$purgetoken;
}
/**
* Compare a pair of purge tokens.
*
* If the two tokens are identical, then the return value is 0.
* If the time component of token A is newer than token B, then a positive value is returned.
* If the time component of token B is newer than token A, then a negative value is returned.
*
* Note: This function is intended for use from within the Cache API only and not by plugins, or cache stores.
*
* @param string $tokena
* @param string $tokenb
* @return int
*/
public static function compare_purge_tokens($tokena, $tokenb) {
if ($tokena === $tokenb) {
// There is an exact match.
return 0;
}
// The token for when the cache was last invalidated.
list($atime) = explode('-', "{$tokena}-", 2);
// The token for this cache.
list($btime) = explode('-', "{$tokenb}-", 2);
if ($atime >= $btime) {
// Token A is newer.
return 1;
} else {
// Token A is older.
return -1;
}
}
/**
* Subclasses may support purging cache of all data belonging to the
* current user.
*/
public function purge_current_user() {
}
}
/**
* An application cache.
*
* This class is used for application caches returned by the cache::make methods.
* On top of the standard functionality it also allows locking to be required and or manually operated.
*
* This cache class should never be interacted with directly. Instead you should always use the cache::make methods.
* It is technically possible to call those methods through this class however there is no guarantee that you will get an
* instance of this class back again.
*
* @internal don't use me directly.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cache_application extends cache implements cache_loader_with_locking {
/**
* Lock identifier.
* This is used to ensure the lock belongs to the cache instance + definition + user.
* @var string
*/
protected $lockidentifier;
/**
* Gets set to true if the cache's primary store natively supports locking.
* If it does then we use that, otherwise we need to instantiate a second store to use for locking.
* @var cache_store
*/
protected $nativelocking = null;
/**
* Gets set to true if the cache is going to be using locking.
* This isn't a requirement, it doesn't need to use locking (most won't) and this bool is used to quickly check things.
* If required then locking will be forced for the get|set|delete operation.
* @var bool
*/
protected $requirelocking = false;
/**
* Gets set to true if the cache must use read locking (get|has).
* @var bool
*/
protected $requirelockingread = false;
/**
* Gets set to true if the cache must use write locking (set|delete)
* @var bool
*/
protected $requirelockingwrite = false;
/**
* Gets set to a cache_store to use for locking if the caches primary store doesn't support locking natively.
* @var cache_lock_interface
*/
protected $cachelockinstance;
/**
* Overrides the cache construct method.
*
* You should not call this method from your code, instead you should use the cache::make methods.
*
* @param cache_definition $definition
* @param cache_store $store
* @param cache_loader|cache_data_source $loader
*/
public function __construct(cache_definition $definition, cache_store $store, $loader = null) {
parent::__construct($definition, $store, $loader);
$this->nativelocking = $this->store_supports_native_locking();
if ($definition->require_locking()) {
$this->requirelocking = true;
$this->requirelockingread = $definition->require_locking_read();
$this->requirelockingwrite = $definition->require_locking_write();
}
$this->handle_invalidation_events();
}
/**
* Returns the identifier to use
*
* @staticvar int $instances Counts the number of instances. Used as part of the lock identifier.
* @return string
*/
public function get_identifier() {
static $instances = 0;
if ($this->lockidentifier === null) {
$this->lockidentifier = md5(
$this->get_definition()->generate_definition_hash() .
sesskey() .
$instances++ .
'cache_application'
);
}
return $this->lockidentifier;
}
/**
* Fixes the instance up after a clone.
*/
public function __clone() {
// Force a new idenfitier.
$this->lockidentifier = null;
}
/**
* Acquires a lock on the given key.
*
* This is done automatically if the definition requires it.
* It is recommended to use a definition if you want to have locking although it is possible to do locking without having
* it required by the definition.
* The problem with such an approach is that you cannot ensure that code will consistently use locking. You will need to
* rely on the integrators review skills.
*
* @param string|int $key The key as given to get|set|delete
* @return bool Returns true if the lock could be acquired, false otherwise.
*/
public function acquire_lock($key) {
$key = $this->parse_key($key);
if ($this->nativelocking) {
return $this->get_store()->acquire_lock($key, $this->get_identifier());
} else {
$this->ensure_cachelock_available();
return $this->cachelockinstance->lock($key, $this->get_identifier());
}
}
/**
* Checks if this cache has a lock on the given key.
*
* @param string|int $key The key as given to get|set|delete
* @return bool|null Returns true if there is a lock and this cache has it, null if no one has a lock on that key, false if
* someone else has the lock.
*/
public function check_lock_state($key) {
$key = $this->parse_key($key);
if ($this->nativelocking) {
return $this->get_store()->check_lock_state($key, $this->get_identifier());
} else {
$this->ensure_cachelock_available();
return $this->cachelockinstance->check_state($key, $this->get_identifier());
}
}
/**
* Releases the lock this cache has on the given key
*
* @param string|int $key
* @return bool True if the operation succeeded, false otherwise.
*/
public function release_lock($key) {
$key = $this->parse_key($key);
if ($this->nativelocking) {
return $this->get_store()->release_lock($key, $this->get_identifier());
} else {
$this->ensure_cachelock_available();
return $this->cachelockinstance->unlock($key, $this->get_identifier());
}
}
/**
* Ensure that the dedicated lock store is ready to go.
*
* This should only happen if the cache store doesn't natively support it.
*/
protected function ensure_cachelock_available() {
if ($this->cachelockinstance === null) {
$this->cachelockinstance = cache_helper::get_cachelock_for_store($this->get_store());
}
}
/**
* Sends a key => value pair to the cache.
*
* <code>
* // This code will add four entries to the cache, one for each url.
* $cache->set('main', 'http://moodle.org');
* $cache->set('docs', 'http://docs.moodle.org');
* $cache->set('tracker', 'http://tracker.moodle.org');
* $cache->set('qa', 'http://qa.moodle.net');
* </code>
*
* @param string|int $key The key for the data being requested.
* @param mixed $data The data to set against the key.
* @return bool True on success, false otherwise.
*/
public function set($key, $data) {
if ($this->requirelockingwrite && !$this->acquire_lock($key)) {
return false;
}
$result = parent::set($key, $data);
if ($this->requirelockingwrite && !$this->release_lock($key)) {
debugging('Failed to release cache lock on set operation... this should not happen.', DEBUG_DEVELOPER);
}
return $result;
}
/**
* Sends several key => value pairs to the cache.
*
* Using this function comes with potential performance implications.
* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
* the equivalent singular method for each item provided.
* This should not deter you from using this function as there is a performance benefit in situations where the cache store
* does support it, but you should be aware of this fact.
*
* <code>
* // This code will add four entries to the cache, one for each url.
* $cache->set_many(array(
* 'main' => 'http://moodle.org',
* 'docs' => 'http://docs.moodle.org',
* 'tracker' => 'http://tracker.moodle.org',
* 'qa' => ''http://qa.moodle.net'
* ));
* </code>
*
* @param array $keyvaluearray An array of key => value pairs to send to the cache.
* @return int The number of items successfully set. It is up to the developer to check this matches the number of items.
* ... if they care that is.
*/
public function set_many(array $keyvaluearray) {
if ($this->requirelockingwrite) {
$locks = array();
foreach ($keyvaluearray as $id => $pair) {
$key = $pair['key'];
if ($this->acquire_lock($key)) {
$locks[] = $key;
} else {
unset($keyvaluearray[$id]);
}
}
}
$result = parent::set_many($keyvaluearray);
if ($this->requirelockingwrite) {
foreach ($locks as $key) {
if ($this->release_lock($key)) {
debugging('Failed to release cache lock on set_many operation... this should not happen.', DEBUG_DEVELOPER);
}
}
}
return $result;
}
/**
* Retrieves the value for the given key from the cache.
*
* @param string|int $key The key for the data being requested.
* @param int $strictness One of IGNORE_MISSING | MUST_EXIST
* @return mixed|false The data from the cache or false if the key did not exist within the cache.
*/
public function get($key, $strictness = IGNORE_MISSING) {
if ($this->requirelockingread && $this->check_lock_state($key) === false) {
// Read locking required and someone else has the read lock.
return false;
}
return parent::get($key, $strictness);
}
/**
* Retrieves an array of values for an array of keys.
*
* Using this function comes with potential performance implications.
* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
* the equivalent singular method for each item provided.
* This should not deter you from using this function as there is a performance benefit in situations where the cache store
* does support it, but you should be aware of this fact.
*
* @param array $keys The keys of the data being requested.
* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.
* @return array An array of key value pairs for the items that could be retrieved from the cache.
* If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown.
* Otherwise any key that did not exist will have a data value of false within the results.
* @throws coding_exception
*/
public function get_many(array $keys, $strictness = IGNORE_MISSING) {
if ($this->requirelockingread) {
foreach ($keys as $id => $key) {
$lock =$this->acquire_lock($key);
if (!$lock) {
if ($strictness === MUST_EXIST) {
throw new coding_exception('Could not acquire read locks for all of the items being requested.');
} else {
// Can't return this as we couldn't get a read lock.
unset($keys[$id]);
}
}
}
}
return parent::get_many($keys, $strictness);
}
/**
* Delete the given key from the cache.
*
* @param string|int $key The key to delete.
* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
* @return bool True of success, false otherwise.
*/
public function delete($key, $recurse = true) {
if ($this->requirelockingwrite && !$this->acquire_lock($key)) {
return false;
}
$result = parent::delete($key, $recurse);
if ($this->requirelockingwrite && !$this->release_lock($key)) {
debugging('Failed to release cache lock on delete operation... this should not happen.', DEBUG_DEVELOPER);
}
return $result;
}
/**
* Delete all of the given keys from the cache.
*
* @param array $keys The key to delete.
* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
* @return int The number of items successfully deleted.
*/
public function delete_many(array $keys, $recurse = true) {
if ($this->requirelockingwrite) {
$locks = array();
foreach ($keys as $id => $key) {
if ($this->acquire_lock($key)) {
$locks[] = $key;
} else {
unset($keys[$id]);
}
}
}
$result = parent::delete_many($keys, $recurse);
if ($this->requirelockingwrite) {
foreach ($locks as $key) {
if ($this->release_lock($key)) {
debugging('Failed to release cache lock on delete_many operation... this should not happen.', DEBUG_DEVELOPER);
}
}
}
return $result;
}
}
/**
* A session cache.
*
* This class is used for session caches returned by the cache::make methods.
*
* It differs from the application loader in a couple of noteable ways:
* 1. Sessions are always expected to exist.
* Because of this we don't ever use the static acceleration array.
* 2. Session data for a loader instance (store + definition) is consolidate into a
* single array for storage within the store.
* Along with this we embed a lastaccessed time with the data. This way we can
* check sessions for a last access time.
* 3. Session stores are required to support key searching and must
* implement cache_is_searchable. This ensures stores used for the cache can be
* targetted for garbage collection of session data.
*
* This cache class should never be interacted with directly. Instead you should always use the cache::make methods.
* It is technically possible to call those methods through this class however there is no guarantee that you will get an
* instance of this class back again.
*
* @todo we should support locking in the session as well. Should be pretty simple to set up.
*
* @internal don't use me directly.
* @method cache_store|cache_is_searchable get_store() Returns the cache store which must implement both cache_is_searchable.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cache_session extends cache {
/**
* The user the session has been established for.
* @var int
*/
protected static $loadeduserid = null;
/**
* The userid this cache is currently using.
* @var int
*/
protected $currentuserid = null;
/**
* The session id we are currently using.
* @var array
*/
protected $sessionid = null;
/**
* The session data for the above session id.
* @var array
*/
protected $session = null;
/**
* Constant used to prefix keys.
*/
const KEY_PREFIX = 'sess_';
/**
* This is the key used to track last access.
*/
const LASTACCESS = '__lastaccess__';
/**
* Override the cache::construct method.
*
* This function gets overriden so that we can process any invalidation events if need be.
* If the definition doesn't have any invalidation events then this occurs exactly as it would for the cache class.
* Otherwise we look at the last invalidation time and then check the invalidation data for events that have occured
* between then now.
*
* You should not call this method from your code, instead you should use the cache::make methods.
*
* @param cache_definition $definition
* @param cache_store $store
* @param cache_loader|cache_data_source $loader
*/
public function __construct(cache_definition $definition, cache_store $store, $loader = null) {
// First up copy the loadeduserid to the current user id.
$this->currentuserid = self::$loadeduserid;
$this->set_session_id();
parent::__construct($definition, $store, $loader);
// This will trigger check tracked user. If this gets removed a call to that will need to be added here in its place.
$this->set(self::LASTACCESS, cache::now());
$this->handle_invalidation_events();
}
/**
* Sets the session id for the loader.
*/
protected function set_session_id() {
$this->sessionid = preg_replace('#[^a-zA-Z0-9_]#', '_', session_id());
}
/**
* Returns the prefix used for all keys.
* @return string
*/
protected function get_key_prefix() {
return 'u'.$this->currentuserid.'_'.$this->sessionid;
}
/**
* Parses the key turning it into a string (or array is required) suitable to be passed to the cache store.
*
* This function is called for every operation that uses keys. For this reason we use this function to also check
* that the current user is the same as the user who last used this cache.
*
* On top of that if prepends the string 'sess_' to the start of all keys. The _ ensures things are easily identifiable.
*
* @param string|int $key As passed to get|set|delete etc.
* @return string|array String unless the store supports multi-identifiers in which case an array if returned.
*/
protected function parse_key($key) {
$prefix = $this->get_key_prefix();
if ($key === self::LASTACCESS) {
return $key.$prefix;
}
return $prefix.'_'.parent::parse_key($key);
}
/**
* Check that this cache instance is tracking the current user.
*/
protected function check_tracked_user() {
if (isset($_SESSION['USER']->id) && $_SESSION['USER']->id !== null) {
// Get the id of the current user.
$new = $_SESSION['USER']->id;
} else {
// No user set up yet.
$new = 0;
}
if ($new !== self::$loadeduserid) {
// The current user doesn't match the tracked userid for this request.
if (!is_null(self::$loadeduserid)) {
// Purge the data we have for the old user.
// This way we don't bloat the session.
$this->purge();
}
self::$loadeduserid = $new;
$this->currentuserid = $new;
} else if ($new !== $this->currentuserid) {
// The current user matches the loaded user but not the user last used by this cache.
$this->purge_current_user();
$this->currentuserid = $new;
}
}
/**
* Purges the session cache of all data belonging to the current user.
*/
public function purge_current_user() {
$keys = $this->get_store()->find_by_prefix($this->get_key_prefix());
$this->get_store()->delete_many($keys);
}
/**
* Retrieves the value for the given key from the cache.
*
* @param string|int $key The key for the data being requested.
* It can be any structure although using a scalar string or int is recommended in the interests of performance.
* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
* @param int $strictness One of IGNORE_MISSING | MUST_EXIST
* @return mixed|false The data from the cache or false if the key did not exist within the cache.
* @throws coding_exception
*/
public function get($key, $strictness = IGNORE_MISSING) {
// Check the tracked user.
$this->check_tracked_user();
// 2. Parse the key.
$parsedkey = $this->parse_key($key);
// 3. Get it from the store.
$result = $this->get_store()->get($parsedkey);
if ($result !== false) {
if ($result instanceof cache_ttl_wrapper) {
if ($result->has_expired()) {
$this->get_store()->delete($parsedkey);
$result = false;
} else {
$result = $result->data;
}
}
if ($result instanceof cache_cached_object) {
$result = $result->restore_object();
}
}
// 4. Load if from the loader/datasource if we don't already have it.
if ($result === false) {
if ($this->perfdebug) {
cache_helper::record_cache_miss($this->get_store(), $this->get_definition());
}
if ($this->get_loader() !== false) {
// We must pass the original (unparsed) key to the next loader in the chain.
// The next loader will parse the key as it sees fit. It may be parsed differently
// depending upon the capabilities of the store associated with the loader.
$result = $this->get_loader()->get($key);
} else if ($this->get_datasource() !== false) {
$result = $this->get_datasource()->load_for_cache($key);
}
// 5. Set it to the store if we got it from the loader/datasource.
if ($result !== false) {
$this->set($key, $result);
}
} else if ($this->perfdebug) {
cache_helper::record_cache_hit($this->get_store(), $this->get_definition());
}
// 5. Validate strictness.
if ($strictness === MUST_EXIST && $result === false) {
throw new coding_exception('Requested key did not exist in any cache stores and could not be loaded.');
}
// 6. Make sure we don't pass back anything that could be a reference.
// We don't want people modifying the data in the cache.
if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($result)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$result = $this->unref($result);
}
return $result;
}
/**
* Sends a key => value pair to the cache.
*
* <code>
* // This code will add four entries to the cache, one for each url.
* $cache->set('main', 'http://moodle.org');
* $cache->set('docs', 'http://docs.moodle.org');
* $cache->set('tracker', 'http://tracker.moodle.org');
* $cache->set('qa', 'http://qa.moodle.net');
* </code>
*
* @param string|int $key The key for the data being requested.
* It can be any structure although using a scalar string or int is recommended in the interests of performance.
* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
* @param mixed $data The data to set against the key.
* @return bool True on success, false otherwise.
*/
public function set($key, $data) {
$this->check_tracked_user();
$loader = $this->get_loader();
if ($loader !== false) {
// We have a loader available set it there as well.
// We have to let the loader do its own parsing of data as it may be unique.
$loader->set($key, $data);
}
if ($this->perfdebug) {
cache_helper::record_cache_set($this->get_store(), $this->get_definition());
}
if (is_object($data) && $data instanceof cacheable_object) {
$data = new cache_cached_object($data);
} else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($data)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$data = $this->unref($data);
}
// We dont' support native TTL here as we consolidate data for sessions.
if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {
$data = new cache_ttl_wrapper($data, $this->get_definition()->get_ttl());
}
return $this->get_store()->set($this->parse_key($key), $data);
}
/**
* Delete the given key from the cache.
*
* @param string|int $key The key to delete.
* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
* @return bool True of success, false otherwise.
*/
public function delete($key, $recurse = true) {
$parsedkey = $this->parse_key($key);
if ($recurse && $this->get_loader() !== false) {
// Delete from the bottom of the stack first.
$this->get_loader()->delete($key, $recurse);
}
return $this->get_store()->delete($parsedkey);
}
/**
* Retrieves an array of values for an array of keys.
*
* Using this function comes with potential performance implications.
* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
* the equivalent singular method for each item provided.
* This should not deter you from using this function as there is a performance benefit in situations where the cache store
* does support it, but you should be aware of this fact.
*
* @param array $keys The keys of the data being requested.
* Each key can be any structure although using a scalar string or int is recommended in the interests of performance.
* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.
* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.
* @return array An array of key value pairs for the items that could be retrieved from the cache.
* If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown.
* Otherwise any key that did not exist will have a data value of false within the results.
* @throws coding_exception
*/
public function get_many(array $keys, $strictness = IGNORE_MISSING) {
$this->check_tracked_user();
$parsedkeys = array();
$keymap = array();
foreach ($keys as $key) {
$parsedkey = $this->parse_key($key);
$parsedkeys[$key] = $parsedkey;
$keymap[$parsedkey] = $key;
}
$result = $this->get_store()->get_many($parsedkeys);
$return = array();
$missingkeys = array();
$hasmissingkeys = false;
foreach ($result as $parsedkey => $value) {
$key = $keymap[$parsedkey];
if ($value instanceof cache_ttl_wrapper) {
/* @var cache_ttl_wrapper $value */
if ($value->has_expired()) {
$this->delete($keymap[$parsedkey]);
$value = false;
} else {
$value = $value->data;
}
}
if ($value instanceof cache_cached_object) {
/* @var cache_cached_object $value */
$value = $value->restore_object();
} else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($value)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$value = $this->unref($value);
}
$return[$key] = $value;
if ($value === false) {
$hasmissingkeys = true;
$missingkeys[$parsedkey] = $key;
}
}
if ($hasmissingkeys) {
// We've got missing keys - we've got to check any loaders or data sources.
$loader = $this->get_loader();
$datasource = $this->get_datasource();
if ($loader !== false) {
foreach ($loader->get_many($missingkeys) as $key => $value) {
if ($value !== false) {
$return[$key] = $value;
unset($missingkeys[$parsedkeys[$key]]);
}
}
}
$hasmissingkeys = count($missingkeys) > 0;
if ($datasource !== false && $hasmissingkeys) {
// We're still missing keys but we've got a datasource.
foreach ($datasource->load_many_for_cache($missingkeys) as $key => $value) {
if ($value !== false) {
$return[$key] = $value;
unset($missingkeys[$parsedkeys[$key]]);
}
}
$hasmissingkeys = count($missingkeys) > 0;
}
}
if ($hasmissingkeys && $strictness === MUST_EXIST) {
throw new coding_exception('Requested key did not exist in any cache stores and could not be loaded.');
}
if ($this->perfdebug) {
$hits = 0;
$misses = 0;
foreach ($return as $value) {
if ($value === false) {
$misses++;
} else {
$hits++;
}
}
cache_helper::record_cache_hit($this->get_store(), $this->get_definition(), $hits);
cache_helper::record_cache_miss($this->get_store(), $this->get_definition(), $misses);
}
return $return;
}
/**
* Delete all of the given keys from the cache.
*
* @param array $keys The key to delete.
* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
* @return int The number of items successfully deleted.
*/
public function delete_many(array $keys, $recurse = true) {
$parsedkeys = array_map(array($this, 'parse_key'), $keys);
if ($recurse && $this->get_loader() !== false) {
// Delete from the bottom of the stack first.
$this->get_loader()->delete_many($keys, $recurse);
}
return $this->get_store()->delete_many($parsedkeys);
}
/**
* Sends several key => value pairs to the cache.
*
* Using this function comes with potential performance implications.
* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
* the equivalent singular method for each item provided.
* This should not deter you from using this function as there is a performance benefit in situations where the cache store
* does support it, but you should be aware of this fact.
*
* <code>
* // This code will add four entries to the cache, one for each url.
* $cache->set_many(array(
* 'main' => 'http://moodle.org',
* 'docs' => 'http://docs.moodle.org',
* 'tracker' => 'http://tracker.moodle.org',
* 'qa' => ''http://qa.moodle.net'
* ));
* </code>
*
* @param array $keyvaluearray An array of key => value pairs to send to the cache.
* @return int The number of items successfully set. It is up to the developer to check this matches the number of items.
* ... if they care that is.
*/
public function set_many(array $keyvaluearray) {
$this->check_tracked_user();
$loader = $this->get_loader();
if ($loader !== false) {
// We have a loader available set it there as well.
// We have to let the loader do its own parsing of data as it may be unique.
$loader->set_many($keyvaluearray);
}
$data = array();
$definitionid = $this->get_definition()->get_ttl();
$simulatettl = $this->has_a_ttl() && !$this->store_supports_native_ttl();
foreach ($keyvaluearray as $key => $value) {
if (is_object($value) && $value instanceof cacheable_object) {
$value = new cache_cached_object($value);
} else if (!$this->get_store()->supports_dereferencing_objects() && !is_scalar($value)) {
// If data is an object it will be a reference.
// If data is an array if may contain references.
// We want to break references so that the cache cannot be modified outside of itself.
// Call the function to unreference it (in the best way possible).
$value = $this->unref($value);
}
if ($simulatettl) {
$value = new cache_ttl_wrapper($value, $definitionid);
}
$data[$key] = array(
'key' => $this->parse_key($key),
'value' => $value
);
}
$successfullyset = $this->get_store()->set_many($data);
if ($this->perfdebug && $successfullyset) {
cache_helper::record_cache_set($this->get_store(), $this->get_definition(), $successfullyset);
}
return $successfullyset;
}
/**
* Purges the cache store, and loader if there is one.
*
* @return bool True on success, false otherwise
*/
public function purge() {
$this->get_store()->purge();
if ($this->get_loader()) {
$this->get_loader()->purge();
}
return true;
}
/**
* Test is a cache has a key.
*
* The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the
* test and any subsequent action (get, set, delete etc).
* Instead it is recommended to write your code in such a way they it performs the following steps:
* <ol>
* <li>Attempt to retrieve the information.</li>
* <li>Generate the information.</li>
* <li>Attempt to set the information</li>
* </ol>
*
* Its also worth mentioning that not all stores support key tests.
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
* Just one more reason you should not use these methods unless you have a very good reason to do so.
*
* @param string|int $key
* @param bool $tryloadifpossible If set to true, the cache doesn't contain the key, and there is another cache loader or
* data source then the code will try load the key value from the next item in the chain.
* @return bool True if the cache has the requested key, false otherwise.
*/
public function has($key, $tryloadifpossible = false) {
$this->check_tracked_user();
$parsedkey = $this->parse_key($key);
$store = $this->get_store();
if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {
// The data has a TTL and the store doesn't support it natively.
// We must fetch the data and expect a ttl wrapper.
$data = $store->get($parsedkey);
$has = ($data instanceof cache_ttl_wrapper && !$data->has_expired());
} else if (!$this->store_supports_key_awareness()) {
// The store doesn't support key awareness, get the data and check it manually... puke.
// Either no TTL is set of the store supports its handling natively.
$data = $store->get($parsedkey);
$has = ($data !== false);
} else {
// The store supports key awareness, this is easy!
// Either no TTL is set of the store supports its handling natively.
/* @var cache_store|cache_is_key_aware $store */
$has = $store->has($parsedkey);
}
if (!$has && $tryloadifpossible) {
$result = null;
if ($this->get_loader() !== false) {
$result = $this->get_loader()->get($parsedkey);
} else if ($this->get_datasource() !== null) {
$result = $this->get_datasource()->load_for_cache($key);
}
$has = ($result !== null);
if ($has) {
$this->set($key, $result);
}
}
return $has;
}
/**
* Test is a cache has all of the given keys.
*
* It is strongly recommended to avoid the use of this function if not absolutely required.
* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
*
* Its also worth mentioning that not all stores support key tests.
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
* Just one more reason you should not use these methods unless you have a very good reason to do so.
*
* @param array $keys
* @return bool True if the cache has all of the given keys, false otherwise.
*/
public function has_all(array $keys) {
$this->check_tracked_user();
if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {
foreach ($keys as $key) {
if (!$this->has($key)) {
return false;
}
}
return true;
}
// The cache must be key aware and if support native ttl if it a ttl is set.
/* @var cache_store|cache_is_key_aware $store */
$store = $this->get_store();
return $store->has_all(array_map(array($this, 'parse_key'), $keys));
}
/**
* Test if a cache has at least one of the given keys.
*
* It is strongly recommended to avoid the use of this function if not absolutely required.
* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
*
* Its also worth mentioning that not all stores support key tests.
* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
* Just one more reason you should not use these methods unless you have a very good reason to do so.
*
* @param array $keys
* @return bool True if the cache has at least one of the given keys
*/
public function has_any(array $keys) {
if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {
foreach ($keys as $key) {
if ($this->has($key)) {
return true;
}
}
return false;
}
/* @var cache_store|cache_is_key_aware $store */
$store = $this->get_store();
return $store->has_any(array_map(array($this, 'parse_key'), $keys));
}
/**
* The session loader never uses static acceleration.
* Instead it stores things in the static $session variable. Shared between all session loaders.
*
* @return bool
*/
protected function use_static_acceleration() {
return false;
}
}
/**
* An request cache.
*
* This class is used for request caches returned by the cache::make methods.
*
* This cache class should never be interacted with directly. Instead you should always use the cache::make methods.
* It is technically possible to call those methods through this class however there is no guarantee that you will get an
* instance of this class back again.
*
* @internal don't use me directly.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cache_request extends cache {
// This comment appeases code pre-checker ;) !
}